1. Field of the Invention
The invention is related to the field of variable diameter pulleys and in particular to a variable diameter pulley having a plurality of discrete belt supporting members arranged in a circular pattern.
2. Description of the Prior Art
Variable diameter pulleys of the type taught by Kumm in U.S. Pat. Nos. 4,295,836, 4,591,351, and 4,768,966, have a plurality of belt supporting members arranged in a circular pattern about an axis of rotation. The diameter of this circular pattern is the effective diameter of the variable diameter pulley and is variable as a function of the rotational orientation between two (2) pairs of juxtaposed disk members which support the ends of the belt support members. The belt support members are equally spaced about the circumference of a circular pattern and only make line contact with a drive belt at spatially separated locations. As a result, the surface engaged by the drive belt is effectively the same as a multi-faced wheel having a plurality of flat belt engaging surfaces with relatively sharp corners. FIG. 1 is an exaggerated example inn which the circular pattern 10 is formed by six (6) equally spaced belt supporting members 12 which effectively occupy the corner positions of a multi-faced geometrical FIG. 14 which, in FIG. 1, is a hexagon. A drive belt 16 engaging this hexagonally-shaped surface will experience relatively sharp bends at the individual belt engaging members which are greater than the curvature of the circular pattern 10 defined by the six belt supporting members 12. This will cause excessive stress on the drive belt reducing its life expectancy. The effective multi-faced pattern resulting from the spatially separated belt supporting members will also result in excessive noise being generated at the drive belt/pulley interface.
The invention is directed to extendible elements which span the spaces between the individual belt supporting members and present to the drive belt 16 a belt engaging surface which eliminates the sharp corners and makes the belt engaging surfaces of the variable diameter pulley more closely approximate a cylindrical surface.